May or June Beetle — Pyllophaga spp

Distant: Skunk and raccoon activity may be the first sign of a grub problem.
The turf will be dug-up and flipped-over during the night. The damaged area will get larger each night.
Another symptom of a grub infestation is when turf becomes thin and sometimes dies in patches.

Up close: Dead patches or large areas of thinning, browning or dead turf. The grass can often be pulled back easily because most of the root system has been consumed by grubs.

Distant: Skunk and raccoon activity may be the first sign of a grub problem.
The turf will be dug-up and flipped-over during the night. The damaged area will get larger each night.
Another symptom of a grub infestation is when turf becomes thin and sometimes dies in patches.

Up close: Dead patches or large areas of thinning, browning or dead turf. The grass can often be pulled back easily because most of the root system has been consumed by grubs.

Time of year when damage appears: March to October

Host: All grass types

Site: Lawns and most types of non-irrigated turf. June beetle grubs and damage are unusual in irrigated lawns and golf course fairways, tees and greens.

Description of damaging stage: 0.5 to 1.5 inch long C-shaped white grubs. They have 6 legs, a brown head capsule, and visible chewing mouthparts.
Damage will generally only occur when some of them are at least a ˝ inch long but there may be a range of sizes of grubs present.

Other Stages and Life History: The adults are usually dark brown but can be black, tan or a dark chestnut color. They vary in length from 0.5 to 1.0 inch long, and tend to be rounded and robust.
The term ‘May or June beetles’ refers to some 10 different species of beetles in the genus Phyllophaga, that are known to injure turfgrass. Adults are most active just before and after sunset in May or June.
They are attracted to lights. Eggs are laid, and hatch in June to early July. The larvae feed on grass, broadleaf weed, tree and shrub roots, and mature in the soil. Unlike the other white grub pests which only have one generation per year, May or June beetle grubs require 2 or 3 years in the soil to fully develop.

Notes: Depending on where you live in the country, the adults are called May beetles, June beetles or June bugs. They are native to North America and are typically found in low numbers anytime you dig in turf or in a landscape planting. It is unusual to see turf damage from June beetle grubs. Dead patches in lawns are much more likely to be caused by European chafer or Japanese beetle. When fully grown, June beetle grubs are much larger than Japanese beetle or European chafer. This makes them even more attractive to skunks to and raccoons. Fortunately, it is rare for lawns to harbor enough June beetle grubs to attract skunks.

Sampling: Dig a 1 ft2 area of turf down about 3 inches and sort through the roots and soil to look for grubs. Do this in several spots in the yard close to and in the dying patches. If the removed turf is kept moist, and watered immediately after putting it back in place, it should re-establish. Sample around the edges of dead patches of turf instead of in the center of the dead patch. If an average of 1 or 2 June beetle grubs per ft2 is found an insecticide application may be warranted.

Preventing Pest Injury to Turfgrass: Home lawns, recreational turf and golf course roughs can be managed to avoid insect injury without insecticides by using proper fertility, mowing at a height of 3.0 to 4.0 inches, and watering during dry periods. This will build a dense stand of turf and a diverse community of insects that will keep turf pests under control. All lawns in Michigan will typically start off lush and green in the spring and will go dormant and turn brown during periods of little rain. Information on the use of insecticides to treat turf pest problems is only meant to be used for the unusual cases where turf damage from pests becomes unacceptable. Even then, insecticides should only be used in areas of a lawn with severe turf damage, and only until a dense turf is re-established.

Using insecticides: Use insecticides judiciously, temporarily, and only in response to unacceptable turf injury. Many insecticides are poisonous if ingested, and therefore must be stored in places where they cannot be found by children. Use the rate recommended on the label for the pest you are attempting to control. Wear rubber gloves, safety glasses (or goggles), rubber boots, long pants and long sleeved shirts when mixing and applying insecticides. The most caution is needed when mixing a concentrated insecticide in water, because skin contact with the concentrated insecticide in the original container is more dangerous than contact with the diluted insecticide after mixing. Water the turf immediately after applying the insecticide to wash it to the base of the plants or into the soil and allow the turf to dry before allowing access by people and pets.

Chemical Control of Grubs: There are 2 types of chemicals that can be used for grub control: curative products (carbaryl and triclorfon) and preventive products (neonicotinoid insecticides such as imidacloprid, thiamethoxam, clothianidin and the anthranilic diamide insecticide, chlorantraniliprole). Read the ingredient section of the label of the insecticide package to determine which active ingredient is in it. The chemicals listed earlier are by common name. There are a myriad of trade names that these active ingredients are in.

The curative grub compounds work “now” (or at least in the next 7-10 days). They need to be applied at the full rate recommended for grub control and should be watered in immediately after application with a minimum of 1/2 inch of water. See the specific sections for the species of grub you are treating for. They will give about 40-65% grub reduction. Don’t use these too late in the fall as it will take one to two weeks to get to where the grubs are feeding. If it is getting cool, the grubs will not be feeding and will not pick up any of the insecticide. The grubs begin to pupate between mid-May and the beginning of June, depending on the grub species. At that time, they stop feeding and again, will not pick up any insecticide if it is applied too late. It is best to wait and apply a preventive compound for a spring grub problem unless there is a very high population.

The preventive grub compounds are systemic and are absorbed by the roots and moved throughout the grass plant. It takes a while for the materials to be absorbed by the plants and they work best on small grubs. It is important to get the material into the root zone so that it can be picked up by the plant. It is also important to apply it early enough to give the chemical a chance to be picked up by the grass before the grubs become large. When properly applied they will give 90+% control of grubs. They do not kill the grubs present at the time they are applied; they kill the ones that will be developing in 3 – 12 weeks. Ideally, the neonicotinoid applications should be made between June 1 and mid-July and should be watered in with a minimum of 1/2 inch of water. They can be applied as late as mid-August, but it becomes more critical to supply irrigation the later you wait. The effectiveness falls off rapidly after about the 3rd week of August, even with irrigation. Chlorantraniliprole is a relatively new compound for grub control. It is much less water soluble than the neonicotinoids and therefore must be applied much earlier. April to mid-May is the optimum timing for chlorantraniliprole, followed with 1/2 inch of irrigation.